1. Field of the Invention
The present invention relates to an information processing system using a portable terminal unit and a data communication adapter therefor.
2. Description of the Related Art
In recent years, portable terminal units such as hand-held terminals (BUTs) are widely used for managing commodities, reading gas and electric meters, and the like.
Generally, a hand-held terminal has a keyboard to input data, a display such as a liquid crystal display, and a printer. Various data are entered into the hand-held terminal, and the entered data are displayed. Since the hand-held terminal is hand-carried, it is designed to be compact and light. A hand-held terminal often employs a memory card such as an IC card as an external storage medium. The memory card stores data entered into the hand-held terminal. The memory card is usually installed in the hand-held terminal from an upper end or a lower end thereof by a memory card loading mechanism installed therein.
However, the locations of the keyboard, the display, and the printer are more or less limited due to the method of use conditions thereof. Further, the hand-held terminal usually incorporates a battery, a modem for communicating data to a larger apparatus, and a connector for connecting the hand-held terminal to the larger apparatus whose position is generally fixed. Accordingly, the position for inserting the memory card is also limited and the width and thickness of the hand-held terminal may be increased by the installation of the memory card, thus having a negative effect on the compactness of the hand-held terminal.
In addition to designing a hand-held terminal that is compact and light, the hand-held terminal is required to have high-performance, Usually, the hand-held terminal is provided with an optical connector to communicate with a larger apparatus by using a transmission adapter. That is, the data input into the hand-held terminal are transmitted to a larger apparatus by connecting the hand-held terminal to a transmission adapter.
Conventionally, when the hand-held terminal communicates with the higher apparatus, an RS232C interface is used. Further, to reduce the size of the hand-held terminal, the prior art multiplexes RS232C interface signals and uses a pair of light emitting and receiving elements to send and receive data. If the hand-held terminal employs a large capacity memory, it must employ a high-speed interface to transmit data at high speed.
High-speed data transmission can be realized by employing a new interface and a connector dedicated to the interface. Installing these additional elements in addition to the conventional RS232C interface, however, is disadvantageous in terms of the compactness and light weight of the portable terminal unit.
Further, the conventional hand-held terminal is equipped with an electrical connector for connecting an external optional device. For example, a card reader for reading a magnetic card may be attached to the hand-held terminal as an optional device to add a function that is not originally present in the hand-held terminal. In this case, the external optional device is connected to the hand-held terminal with connectors and may be fixed thereto with at least one screw.
The connectors are fixed to the respective apparatuses or to printed circuit boards of the respective apparatuses. When connecting the apparatuses together, the connectors must be accurately positioned in relation to each other. This makes the connection work complicated.
In addition, connection of the external optional device makes the size of the hand-held terminal larger when the position of the connector on the hand-held terminal is not proper.
Incidentally, since the hand-held terminal can be used under various conditions, they should be sealed to prevent moisture or liquids from entering the terminal. The hand-held terminal may have a moisture resistant seal made of, for example, rubber. The seal is generally held between an upper casing and a lower casing of the hand-held terminal.
The lower part of the hand-held terminal may be provided with a connector to be connected to an external device and a jack for charging a battery incorporated in the hand-held terminal. The connector and jack may be provided with a moisture-and-dust-resistant cover made of rubber or resin. When transmitting data to ab external device or when charging the battery, the covers are removed. Since the removed covers may be lost, to prevent this, there may be provided a notch on the casing and a T-shaped projection on the cover. The T-shaped projection of the cover can then be inserted into the notch of the casing, to fix the cover to the casing. The cover is sometimes extended therefrom to cover an interface connector.
However, the prior art that puts rubber between an upper casing and a lower casing provides poor workability and makes the size of the housing of the hand-held terminal larger. That is, the rubber must be made large enough to prevent the rubber from peeling off and moisture from penetrating. Further, if the T-shaped projection of the connector cover is loose in the notch, the projection may easily slip out of the notch of the casing, to cause the cover to be lost and provide poor moisture resistance.
Since the above-described hand-held terminals are usually carried around, they usually employ batteries, in particular, rechargeable batteries, as a power source.
The transmission adapter is interposed between the hand-held terminal and the larger apparatus, to transmit data from the hand-held terminal to the larger apparatus, or from the larger apparatus to the hand-held terminal. The hand-held terminal and transmission adapter may be connected to each other through optical connectors using on interface such as a RS232C interfaces.
When transmitting data to the larger apparatus, the hand-held terminal must be connected to a transmission adapter. While the hand-held terminal is connected to the transmission adapter to transmit data to the larger apparatus, the transmission adapter charges the battery of the hand-held terminal. In this case, the hand-held terminal is provided with a battery charging jack and the transmission adapter has a battery charging terminal. When the hand-held terminal is connected to the transmission adapter, the jack is connected to the terminal to start charging the battery of the hand-held terminal. Power for this charging operation is supplied by a power source circuit in the transmission adapter.
However, the transmission adapter must charge the hand-held terminal, and at the same time, carry out data transmission between the hand-held terminal and the larger apparatus. The charging operation requires a relatively large amount of power, so that the power source of the transmission adapter must have a large capacity, This results in enlarging the power source of the transmission adapter.
It is always required to minimize the hand-held terminal and transmission adapter. If the power source of the transmission adapter in large, the size of the transmission adapter cannot be minimized. Also, when the transmission adapter simultaneously carries out the charging and data transmission operations, the transmission adapter consumes a large amount of power, therby making the power source circuit of the transmission adapter large.